In my previous post, I gave a general overview of what
therapeutic hypothermia (TH) is. You'll remember, it is most often used
for those who experience a sudden cardiac arrest (SCA) and who have
subsequently been revived with CPR. TH is clinically indicated for those
who experience a SCA due to two abnormal heart rhythms: ventricular tachycardia
(V-Tach) and ventricular fibrillation (V-Fib). Other arrhythmias like
asystole (no heartbeat at all) and pulseless electrical activity (there's
electrical conduction going on in the heart but no actual beat) have not shown
to benefit from therapeutic hypothermia.
So now we understand a little bit about the differences in
the arrhythmias when TH is useful. So what are the other qualifications a
patient must meet in order to undergo TH?
Patients who are considered for therapeutic hypothermia have
to meet two kinds of criteria: inclusion criteria and exclusion criteria. As
you might guess, inclusion criteria would include people as candidates.
If any person should fall under any part of the exclusion criteria, they
are no longer considered as a candidate for treatment.
Inclusion criteria for TH are those who have V-Fib or V-Tach
as their initial insulting rhythm, as mentioned earlier. Typically these patients become unconscious very
quickly so an estimated “down-time” is usually no more than 10-15 minutes from
initial insult to the start of CPR.
Further, a patient included for TH should not be down for longer than 60
minutes from initial insult to what is called return of spontaneous circulation
(ROSC). After ROSC, in order for TH to be of any use, the patient must be
comatose. Those who are conscious after
ROSC obviously are in no need of therapeutic hypothermia because there are no
neurological deficits. Patients must
also be intubated with mechanical ventilation and be at least 18 years old.
Exclusion criteria, or those who are not candidates are
those who are pregnant, have known blood clotting disorders (hypothermia
increases blood clotting times which puts hypothermic patients at risk for
bleeding), and those who are comatose for any reason other than cardiac arrest
(head injuries, strokes, etc). Patients
with a known do-not-resuscitate (DNR) status are not candidates for TH, as
their wishes are, obviously, to not be resuscitated.
Therapeutic hypothermia is a wonderful treatment for those who
are candidates to receive it. Clinicians
offering this treatment should be well aware of the inclusion and exclusion
criteria before initiating it on any patient. If you would like more
information, I will place more links below.
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